The Quattro Bolt Locking Mechanism provides unequaled strength by locking the crossbar to the shackle on four sides, maximizing pull resistance. The Boxer has a 16.8mm ultra hardened steel shackle. The pick, pull, and drill resistant M-key cylinder features BumpBlok with rotating dust cover. Five laser cut keys, 1 with an LED micro-light, carrying pouch and disc reminder are included. The crossbar and shackle have protective coatings.